An LCD device includes an LC panel, a backlight unit that irradiates the LC panel from the rear side, and front and rear frames that sandwich therebetween the LC panel. The rear frame supports the backlight unit and may be referred to as backlight chassis. The front frame is disposed in front of the LC panel, and supports the LC panel between the same and the rear frame.
In the LCD device, there is a risk that dust enters through a gap between the LC panel and the front and rear frames to degrade the image quality of the LCD device. Thus, it is needed to provide a structure that prevents the ingress of dust into the LCD device.
Patent Publication-1 describes an LCD device including the structure for preventing the ingress of dust, wherein an elastic spacer is sandwiched between the LC panel and the rear frame. The spacer is made of a soft, elastic urethane foam etc., and has a front surface in contact with the LC panel and a rear surface in contact with the rear frame.
Patent Publication-2 describes an LCD device including an elastic body that supports the LC panel at the rear side thereof. The elastic body has a pointed top that contacts the LC panel, and deforms due to the weight of the LC panel to thereby clog the gap between the LC panel and the elastic body by the repulsive force thereof.
Patent Publication-3 describes an LCD device that includes an elastic member disposed between the LC panel and a mold body configuring the backlight unit. The elastic member has a rear surface attached onto the backlight unit and a front surface in contact with the LC panel at any time, thereby preventing generation of a gap between the LC panel and the elastic member.
Patent Publication-4 describes an LCD device that includes a groove formed on the rear frame and a spacer received in the groove. The spacer is an elastic member of a ring shape or annular shape and supports the LC panel. The spacer is deformed due to the weight of the LC panel to clog the gap between the LC panel and the elastic member rear frame by the repulsive force thereof.
Patent Publication-5 describes an LCD device that includes a groove on the rear frame and a ring-shaped elastic body received in the groove. The elastic body clogs the gap between the LC panel and the rear frame, and at the same time reduces a shock or vibration transferred to the LC panel.
Patent Publication-6 describes an LCD device that includes an LC panel including top and bottom substrates and a spacer for fixing together the front frame having a narrow width and the LC panel. The spacer is fixed onto the front frame or a marginal space of the bottom substrate that protrudes from the top substrate.
The Patent Publications as recited above include:
Patent Publication-1—JP-2000-19529A;
Patent Publication-2—JP-2005-91971A;
Patent Publication-3—JP-2005-275103A;
Patent Publication-4—JP-1998-206828A;
Patent Publication-5—JP-1997-22000A; and
Patent Publication-6—JP-1999-305206A.
The following is the analysis performed by the present inventor before accomplishment of the present invention. There is no recitation in Patent Publication-1 as to whether or not the elastic body disposed between the LC panel and the rear frame in the LCD device is fixed onto either of the LC panel and rear frame. In this case, if the elastic body is not fixed onto at least one of the LC panel and rear frame, the LCD device is liable to the ingress of dust after the LC panel moves in the direction normal to the LC panel, i.e., screen. On the other hand, if the elastic body is fixed onto both LC panel and rear frame, a stress acting on the LC panel and/or rear frame due to a strain or deformation cannot be relieved, thereby possibly causing the LC panel to generate disturbance of light distribution and have a reduced image quality.
In the LCD devices described in Patent Publications-2 to -4, the elastic body is deformed to contact the LC panel due to the repulsion force of the elastic body. This causes acting of a shock or vibration onto the LCD device, and if the LC panel moves in the direction normal to the screen, a gap is momentarily formed between the elastic body and the LC panel, thereby causing the ingress of dust. Moreover, a distortion of parts during assembly of the parts or a deformation of the parts due to a heat stress, if arises, will also cause the occurrence of a gap between the elastic body and the LC panel. Furthermore, a particular shape of the elastic body for preventing the ingress of dust, if employed as in the LCD device described in Patent Publication-2, will reduce the elasticity or flexibility of the elastic body due to the time degradation, to deform the pointed shape of the elastic body and possibly degrade the dimensional accuracy. In this case, a clearance between the parts may be changed to generate the gap, thereby degrading the performance of preventing the ingress of dust.
Furthermore, the range of variation in the dimensional accuracy of the parts as well as the distortion occurring during assembly of the parts may reduce the clearance between the rear frame and the LC panel or may increase the thickness of the elastic body itself, thereby increasing the load acting on the LC panel from the elastic body. In such a case, the LC panel may generate a disturbance of light distribution to degrade the image quality thereof. Although Patent Publication-4 recites that the spacer is disposed within the groove formed on the rear frame, this groove only assists assembly of the ring-shaped spacer to facilitate assembly of the LCD device.
Although Patent Publication-5 describes a groove formed on the rear frame, it is not disclosed that a shock or vibration is applied onto the LCD device, and that a momentary gap occurs between the LC panel and the elastic body.
The LCD device described in Patent Publication-6 uses the spacer for fixing together the front frame having a narrow width and the LC panel. However, prevention of the ingress of dust onto the front surface or rear surface of the LC panel is not disclosed in this publication. This means the dust will enter the LCD device across the surface of the spacer that is not fixed by adhesive.